<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>数学</title>
	<script type="text/javascript">
		res = Math.abs(-89);

		res = Math.round(78.12);

		res = Math.ceil(1.000001);

		res = Math.floor(1.9999);

		res = Math.random();

		res = Math.round(Math.random()*(47-1)+1); 
		//取x到y之间的随机数

		document.write(res);






	</script>
</head>
<body>
	
</body>
</html>